For marine seismic data, the source and receiver ghosts generated by the free surface cause angle dependent frequency and amplitude distortion. For improved interpretation and inversion, these unwanted effects are best corrected in a pre-stack depth image.
Interpreting subtle geologic features in a marine environment requires the associated seismic data to contain both low and high frequencies necessary for high resolution imaging. In general, high-fidelity, low frequency data provides greater penetration of the underlying strata and an associated better illumination of deep targets in addition to providing greater stability and information more important for seismic inversion. Accordingly, it is preferable to obtain a wide bandwidth seismic image.
Achieving wide bandwidth pre-stack depth images from marine seismic data requires overcoming bandwidth limitations imposed by source and receiver ghosts. Recently, many attempts have been made to compensate for source and receiver ghosts such as variable-depth streamer acquisition as described by R. Soubaras and P. Whiting (hereinafter “Soubaras/Whiting”) in their 2011 article entitled “Variable Depth Streamer—The New Broadband Acquisition System,” published in the 81st Annual International Meeting, SEG, Expanded Abstracts, pages 4349-4353 and incorporated herein by reference. They proposed to take advantage of the low noise response of new generation solid streamers and the notch diversity caused by receiver depth variation to give a high quality broadband spectrum.
Continuing with suitable broadband spectrums, the receiver ghosts can be removed in a later processing stage by processing and imaging techniques as described by R. Soubaras (hereinafter “Soubaras”) in his 2010 article entitled “Deghosting by Joint Deconvolution of a Migration and a Mirror Migration,” published in the 81st Annual International Meeting, SEG, Expanded Abstracts, pages 3406-3410, incorporated herein by reference and by R. Soubaras and Y. Lafet in their 2011 article entitled “Variable Depth Streamer Acquisition: Broadband Data for Imaging and Inversion,” published in the 81st Annual International Meeting, SEG, Expanded Abstracts, pages 2364-2368 and incorporated herein by reference. The aforementioned techniques generate an exceptionally sharp and clean wavelet for interpretation with respect to receiver ghosts.
However, removing the source ghosts remains a more difficult task based on the assumption that the sources are excited at a roughly fixed depth, i.e., lack of notch diversity, and with a large shot increment in lateral positions, i.e., severe data aliasing, as generally happens in marine tow-streamer surveys. Further, the existence of ghosts distorts both the migration spectrum and the amplitude versus angle (AVA) relation.
Accordingly, it would be desirable to provide systems and methods that avoid the afore-described problems and drawbacks, and provide compensation for both source and receiver ghosts in a wide bandwidth seismic dataset.